Unit 8 Progress Check MCQs

Which of the following is closest to the calculated wolf population size in 2017 based on the student's claim?

103

Which of the following is the most likely cause of the change in mean aspen height from 1998 to 2010 ?

The reintroduction of wolves led to a decrease in the population of elk, allowing aspen trees to grow taller.

Identify the independent variable for the experimental results shown in Figure 2.

The presence of wolves

A biologist was investigating the effects of herbivory on the amount of nicotine produced by the leaves of tobacco plants (Nicotiana rustica). Six groups of plants were grown from seed in the same greenhouse with identical environmental conditions. Three groups were then each exposed for a different interval of time to tobacco hornworms (Maduca sexta), which feed on the foliage of tobacco plants. The amount of nicotine present in the leaves was measured at the beginning and end of each time interval. As a control, the other three groups were not exposed to hornworms. The results of the experiment are summarized in Table 1.

The dependent variable is the percent change in the amount of nicotine, and the independent variable is the time interval the plants were exposed to the hornworms.

Which of the following best describes the change in coyote behavior in the presence of wolves?

rest --> decreases travel --> no effect hunt --> no effect feeding on carcasses --> increases

Bison in Yellowstone National Park have a food-limited carrying capacity that determines how their population grows. If the population grows too large, some bison will either starve or migrate to search for more food. The park is able to support a maximum population of 4,500 bison. Park conservation officials must watch the population and prevent the bison from overpopulating, since they would migrate to nearby farms, causing agricultural damage and creating hazards to drivers. The bison begin to migrate when the population reaches 4,000 because of competition for food. If the current population size of bison is 3,652 and the maximum growth rate of the population is 0.28, calculate the population size after one year and determine whether the park will need to take measures to control the population. Responses

The population will be 3,845 after a year. The bison will not pose a problem until the following year, and no conservation action will need to take place.

Meerkats live together in groups to help raise and protect their offspring. Meerkat pups are most vulnerable when they are away from their burrow foraging for food. Adult meerkats exhibit sentinel behavior, standing upright and making alarm calls to warn other members in the group that predators are nearby. In a study of meerkat behaviors, scientists observed meerkat foraging groups and recorded the presence or absence of pups along with the frequency of adult sentinel behavior. The scientists determined that sentinel behavior increased when pups were present in the foraging group. Which of the following correctly identifies the dependent and independent variables in the described study? Responses

The presence of pups is the independent variable, and the frequency of sentinel behavior is the dependent variable.

BtBt corn varieties are genetically modified to produce a toxin that specifically kills corn borers, a type of insect that eats and damages corn crops. Insects that are not closely related to corn borers are not affected by the toxin. Figure 1 shows the increasing production of BtBt corn varieties and the change in the use of broad-spectrum pesticides that were the primary means of killing corn borers before the invention of BtBt corn. Figure 1. Relative use of pesticides on corn fields and percent of BtBt corn in crops How do the data in Figure 1 support the alternative hypothesis that increased use of BtBt corn reduces the impact of corn farming on the natural environment? Responses

The toxin in BtBt corn kills only the corn pests, leaving other insects unharmed.

In the mid-1920s, gray wolves, Canis lupus, were eliminated from Yellowstone National Park in the northwestern United States. Over the course of 1995 and 1996, 31 wolves from Canada were relocated to the park. Researchers have tracked the growth of the wolf population from 21 in 1995 to 108 at the end of the study in 2016 (Figure 1). The wolves prey on large herbivores, primarily elk. The carcasses of wolf kills are a valuable food source for coyotes, Canis latrans. When coyotes are feeding on carcasses, they may be chased off the carcass and/or killed by wolves. Coyotes also hunt small mammals for food. Researchers were studying the effect of wolves' presence on the behavior of coyotes. Researchers observed coyotes in a specific area of Yellowstone National Park and recorded the proportion of the coyotes' time spent on five different activities when wolves were present in the study area and when wolves were absent (Figure 2).

17 wolves per year

Figure 1 shows the population fluctuations of phytoplankton and zooplankton in the eastern Pacific Ocean over the course of six years. The major dip in phytoplankton was attributed to a lack of nutrients for phytoplankton. Figure 1. Relative abundance of plankton over time in the eastern equatorial Pacific Ocean Of the following, which explains why the zooplankton also dipped during the same year and then seemed to cycle over the next three years?

The reduction in the phytoplankton population meant that the zooplankton's energy source was drastically reduced, leading to the decrease in the zooplankton population size. After the dip, the phytoplankton provided a steady energy source, and the zooplankton population fluctuated around its carrying capacity.